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BY JUSTIN RAY
Follow the countdown and launch of the ULA Atlas 5 rocket carrying a classified national security satellite. Reload this page for the latest on the launch.

MONDAY, DECEMBER 10, 2007
Its thunderous departure out of Cape Canaveral on Monday afternoon was hard to miss, but the hush-hush ascent of the Atlas 5 rocket was wrapped in an unusual cloak of secrecy as the booster propelled high above Earth a classified spacecraft designed to communicate with spy satellites.

2359 GMT (6:59 p.m. EST)
"ULA is proud to have played a critical role for this important NRO mission, ensuring that our nation has the technology and spaceborne assets needed to acquire intelligence worldwide," said Jim Sponnick, United Launch Alliance vice president of Atlas programs said in tonight's post-launch news release.

"Close teamwork with the NRO Office of Space Launch, the U.S. Air Force Launch and Range Systems Wing and the 45th Space Wing at Cape Canaveral made today's successful mission possible."

2355 GMT (6:55 p.m. EST)
The spent Centaur upper stage for today's launch is creating a stunning view over Cape Canaveral right now. After successfully hauling its clandestine payload into orbit, the upper stage is dumping residual propellant overboard that creates a bright fan-shaped cloud in the night sky as the rocket flies overhead. This is a special treat adding to the beautiful liftoff witnessed nearly two hours ago.

2323 GMT (6:23 p.m. EST)
Today's launch of the Atlas 5 rocket has been declared a success, the NRO just announced!

2210 GMT (5:10 p.m. EST)
And with that, the launch has gone into a news blackout. No further information about the rocket's flight is expected to be reported in real-time.

We'll pass along any additional updates as they become available tonight. Also check back for movie clips and photos of the liftoff.

2203 GMT (5:03 p.m. EST)
T-minus 90 seconds. Launch control system is enabled. The flight termination safety system has been armed.

2203 GMT (5:03 p.m. EST)
T-minus 1 minute, 50 seconds. The automatic computer sequencer is in control of all the critical events through liftoff.

2203 GMT (5:03 p.m. EST)
T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching to internal power. Liquid oxygen and liquid hydrogen topping for Centaur will be stopped in about 10 seconds.

2202 GMT (5:02 p.m. EST)
T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for flight. Also, the RP-1 tank is being pressurized to flight level.

2201 GMT (5:01 p.m. EST)
T-minus 4 minutes and counting. The final phase of afternoon's countdown has begun for the launch of the ULA Atlas 5 rocket on a classified satellite deployment mission for the National Reconnaissance Office! Liftoff is targeted to occur at 5:05 p.m.

2200 GMT (5:00 p.m. EST)
Countdown clocks will resume in one minute. All is in readiness for flight today.

2159 GMT (4:59 p.m. EST)
The ULA launch director and the government mission director each have given their approval to press onward with the countdown.

2158 GMT (4:58 p.m. EST)
No problems were reported by the launch team during the just-completed poll. All systems are in readiness to continue with the countdown for liftoff at 5:05 p.m.

2158 GMT (4:58 p.m. EST)
Launch team polling is underway.

2153 GMT (4:53 p.m. EST)
Coming up in five minutes at 4:58 p.m. EST, the launch team will be polled for a "go" or "no go" to proceed with the count.

2150 GMT (4:50 p.m. EST)
T-minus 4 minutes and holding. The countdown has entered the planned 11-minute hold to give the launch team a chance to review all systems before pressing ahead and sync up with the 5:05 p.m. liftoff time.

2138 GMT (4:38 p.m. EST)
The fuel-fill sequence for the first stage main engine is beginning.

2135 GMT (4:35 p.m. EST)
Thirty minutes to go. Today's launch will be the 12th for an Atlas 5 rocket since debuting in August 2002. The vehicle's flights have featured a very diverse payload list, including NASA space probes to Mars and Pluto, experimental U.S. military spacecraft, spy satellites and several commercial communications craft.

This flight is the first to use the rocket's 401 configuration. The Common Core Booster first stage is outfitted with the RD-180 main engine and no solid rocket boosters, the Centaur upper stage has a single RL10 cryogenic engine and the payload shroud is the four-meter diameter option.

2043 GMT (3:43 p.m. EST)
First stage liquid oxygen tank is about a third full. Chilled to Minus-298 degrees F, the liquid oxygen will be used with RP-1 kerosene by the RD-180 main engine on the first stage during the initial four minutes of flight today. The 25,000 gallons of RP-1 were loaded into the rocket prior today's countdown.

2029 GMT (3:29 p.m. EST)
The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. The Centaur holds about 13,000 gallons of the cryogenic propellant.

2028 GMT (3:28 p.m. EST)
About three-quarters of the Centaur liquid oxygen tank has been filled so far.

2027 GMT (3:27 p.m. EST)
NEW LAUNCH TIME. The launch team is will be retargeting today's liftoff time to 5:05 p.m. EST. The change will ensure the rocket is not launched at time that would take its path too close to another object already in space. The original opening of the launch window is within a COLA, or Collision Avoidance period.

An extra minute will be added to the final built-in hold of the countdown to sync up with the new time.

2025 GMT (3:25 p.m. EST)
The chilldown conditioning of the systems for the first stage liquid oxygen tank have been completed. And a "go" has been given to begin pumping super-cold liquid oxygen into the Atlas 5's first stage. The Atlas liquid oxygen tank is the largest tank to be filled today. It holds about 50,000 gallons of cryogenic oxidizer for the RD-180 main engine.

2008 GMT (3:08 p.m. EST)
Following the thermal conditioning of the transfer pipes, filling of the Centaur upper stage with about 4,300 gallons of liquid oxygen has begun at Cape Canaveral's Complex 41.

The liquid oxygen -- chilled to Minus-298 degrees F -- will be consumed during the launch by the Centaur's single RL10 engine along with liquid hydrogen to be pumped into the stage a little later in the countdown. The Centaur will perform firings today to deliver the secret satellite into the desired orbit.

2001 GMT (3:01 p.m. EST)
The Centaur liquid oxygen pad storage area has been prepped. The next step is conditioning the transfer lines, which is now beginning to prepare the plumbing for flowing the cryogenic oxidizer.

Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 10 minutes during which time the final "go" for launch will be given. All remains targeted for liftoff at 5:04 p.m. EST from Cape Canaveral's Complex 41.

In the next couple of minutes, chilldown thermal conditioning of the mobile launch platform upon which the rocket stands will begin. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket a short time from now.

1924 GMT (2:24 p.m. EST)
T-minus 2 hours and holding. The countdown is entering the first of two planned holds over the course of the afternoon that will lead to the 5:04 p.m. EST launch of Atlas.

This initial pause lasts 30 minutes, giving the some margin in the countdown timeline to deal with technical issues or any work that is running behind. The final hold is scheduled to occur at T-minus 4 minutes and last for 10 minutes.

Despite the conflicting information yesterday and today about the launch time, it now appears 5:04 p.m. is the correct time after all.

The official weather forecast still puts the odds of acceptable conditions at 80 percent. Cumulus clouds and disturbed weather in the form of rainshowers within five miles of the pad are the two concerns.

1830 GMT (1:30 p.m. EST)
Three-and-a-half hours away from launch. There have been some rainshowers moving ashore south of the launch site. But conditions over Complex 41 are looking good right now.

1745 GMT (12:45 p.m. EST)
It is a beautiful day along Florida's east-central coast. Little is known about the progress of the countdown but the launch appears to be on schedule for shortly after 5 p.m.

1600 GMT (11:00 a.m. EST)
Today's publicly announced launch time has been revised to 5:03 p.m. EST (2203 GMT). Our countdown preview below has been corrected to reflect the new time.

MONDAY, DECEMBER 10, 2007
A secretive rocket launch is scheduled to go off this afternoon from Cape Canaveral as a United Launch Alliance Atlas 5 rocket hauls a classified spacecraft into orbit for the U.S. National Reconnaissance Office.

Liftoff is expected shortly after 5 p.m. EST (2200 GMT).

The weather forecast predicts an 80 percent chance of acceptable conditions. The outlook calls for some scattered clouds at 3,000 and 20,000 feet, an easterly breeze of 14-18 knots, good visibility and a temperature in the mid-70s F.

"For launch day, high pressure persists with easterly winds gusting in the mid to upper teens and a small threat of isolated coastal showers. The primary concern for launch day is cumulus cloud rule with the coastal showers," the launch weather team reported.

Based on a typical Atlas countdown, here's what will happen today:

Once the clocks begin ticking a few minutes after 10 a.m. this morning, the launch team will power up the rocket and begin standard pre-flight tests. Crews at the pad will make preparations to systems and equipment before the site is cleared of all personnel.

A planned half-hour hold begins at 2:23 p.m. when the count reaches T-minus 120 minutes. Near the end of the hold, the team will be polled to verify all is in readiness to start fueling the rocket for launch.

Supercold liquid oxygen begins flowing into the Centaur upper stage around 3:10 p.m., followed by the first stage filling about 3:25 p.m. Liquid hydrogen fuel loading for Centaur will be completed a short time later.

A final hold is scheduled at the T-minus 4 minute mark starting at 4:49 p.m. That will give everyone a chance to finish any late work and assess the status of the rocket, payload, Range and weather before proceeding into the last moments of the countdown.

The RD-180 main engine will power the 19-story rocket off the launch pad for a northeastward race up the U.S. Eastern Seaboard toward orbit.

Progress of the launch is expected to enter a news blackout once the vehicle's protective nose cone is jettisoned, a major change from recent NRO spaceflights.

The rocket will fly in the 401 vehicle configuration with a four-meter fairing, no solid rocket boosters and a single-engine Centaur upper stage.

The Atlas 5 traveled from its 30-story Vertical Integration Facility assembly building to the pad at Cape Canaveral's Complex 41 on Sunday morning. A photo gallery is posted here.

A pair of specially-made "trackmobiles" pushed the rocket's 1.4-million pound mobile launching platform along rail tracks for the trip. The platform is what the Atlas 5 sits upon from the time it is stacked in the VIF until the main engine is fired at liftoff. Umbilicals feeding fuel, power and all other lines from the ground to the rocket run through the platform.